The present invention is directed to a process for the continuous production of indene resins. Indene resins can be produced by polymerization of suitable fractions of tar or petro origin with a cationic initiator, such as boron trifluoride or boron trifluoride adducts. Indene-containing hydrocarbon fractions may also be obtained by fractional distillation of water-gas tar and oil-gas tar. In addition to indene, these hydrocarbon fractions may contain coumarone, methyl indene, methyl styrene, styrene, cyclopentadiene, and related compounds. These indene-containing hydrocarbon fractions are polymerized by the addition of acid, presumably to linear polymers. These polymers are generally low in molecular weight (about 1,000 or below) and are fluid above their melting points. The polymers are widely used in surface coatings, printing inks, adhesives, waxed papers, and floor tiles, and as softeners and tackifiers in the rubber industry. See for example "Textbook of Polymer Science", Second Edition by Fred W. Billmeyer, Jr., (Wiley-Interscience 1971), which is hereby incorporated by reference.
While the production of indene resins is known in the art, processes for their production are usually conducted on a discontinuous basis. When a continuous process is desired, the use of a reaction vessel equipped with an agitator has been proposed (cf. German published application No. 1,470,451 and U.S. Pat. No. 2,565,222). These processes have not proven entirely satisfactory because only resins in a narrow softening point range can be produced and conversions are unsatisfactory.
With most of the continuous processes for the polymerization of indene-containing hydrocarbon fractions, reprocessing of the polymerizate (i.e., separation of the catalyst and the solvent from the indene-containing resin) has taken place discontinuously so that the advantages of the continuous polymerization step have never been fully realized. For example, German published application No. 1 470 451 and U.S. Pat. No. 2,565,222 (which are both hereby incorporated by reference) disclose processes in which the separation of the catalyst after polymerization is carried out with adsorbents, such as clay or diatomaceous earth. Clearly, the processes described in these references have the inherent disadvantage that the adsorption medium is eventually exhausted and must be regenerated or changed. When the adsorption medium is changed or regenerated the production of indene-containing resins must be temporarily halted. Hence, it may be seen that the processes of the prior art have taken place discontinuously.
In contrast to the prior art, the present invention is directed to a continuous process for the production of indene resins comprising a series of continuous steps. Because there are no discontinuities in the process of the present invention, the advantages of the continuous polymerization of indene-containing hydrocarbon fractions are fully realized.
As those skilled in the art are aware, the quality of indene resins is determined by the brightness, the softening point and the acid number of the resin. It is desirable that the brightness values lie within the range of 0.5 to 2.0 Barrett (hereafter abbreviated B 0.5 to B 2.0). It is further desirable that the acid numbers of the indene polymers be low, preferably below 0.05. The softening points of the indene resins desired will depend on the intended use of the resins. The prior art is capable only of producing resins in a narrow range of softening points. By contrast, the present invention permits the production of bright indene resins over a wide range of softening points. The softening point of the indene resin produced will depend upon the reaction parameters, and in particular upon the polymerization temperature.
It is therefore a primary object and purpose of the invention to provide a continuous process for the production of indene resins comprising a series of continuous steps.
Another object of the invention is to provide a continuous process for the production of indene resins including continuous separation of the indene resin produced from the catalyst and unreacted hydrocarbon-containing mixture.
Still another object of the invention is to provide a continuous process for the production of very bright indene resins having a softening point range between 0.degree. C. and 170.degree. C. KS (i.e., Kraemer-Sarnow) with very low catalyst consumption.
A further object of the invention is to provide a continuous process for the production of indene resins with brightness values and acid numbers which are more favorable than those which can be obtained by the prior art.
It is another object of this invention to provide a continuous process for the production of indene resins utilizing a relatively short reaction time and yet obtain a high yield of resin.
Other objects and advantages of the invention will become apparent from the detailed description which follows.
The indene polymers produced by the process of the present invention can be used for many of the purposes discussed. As those skilled in the art are aware, the utility to which an indene resin is applied will depend upon the softening range of the resin as well as its brightness value and acid number.